What's the frequency response of vinyl?

If any of you guys were alive in the 1970s :) remember the CD-4 system that RCA used for 4 channel? The LPs were cut as 2 channel records, but had the rear channels imposed on a 42KHz FM carrier that was *also* cut on the record. And this was with 1970s cartridges! (of course there were CD-4 cartridges that they recommended, but a good 2 channel unit would work too).

IOW, exceeding CD bandwidth is a piece of cake. You can do that with cassettes for pete's sake!

I used to believe that 20KHz was tops, based on microscopic visual groove inspection. However, I now have a spectrum analyser, and although it only goes up to 20KHz it shows that some LPs still have signal at 20 KHz, and the signal level is rolling off with frequency at a rate which suggests it would go to zero in the 30-35KHz range.

If you wanted to test this you could play the record at half speed (some TT will do this) and see what you get. If you saw 20KHz that would mean that the LP grooves had 40KHz wiggles. Whether your cartridge and/or speakers and/or ears could handle 40KHz is another matter.

Eldartford,

If you are measuring the output of your phono stage, you better make sure that the phono stage bandwidth is not limiting (mine is rated flat out to 100 kHz). Also, if you are using a moving magnet cartridge other than a Grado, the high inductance of its coils will roll off the treble rapidly, sometimes starting below 20 kHz. This rolloff gets worse with increased load capacitance.

Tafka_steve...Flat to 100KHz is not a big deal for electronics. I doubt that my Shure V15mr cartridge goes that high, but it would still be sensitive at 35KHz. However, please note that I am inferring the maximum frequency from the behavior evident below 20KHz, a range where the frequency response of the cartridge is not an issue. An analogy would be to estimate the distance of a baseball home run by observing the height and trajectory of the ball as it dissapeared over the fence.

Has anyone done the half speed experiment? That would provide the best answer. 16 rpm turntables are not common, but a 45rpm record played at 33 would give some idea.

Here's the link to the article about Stan Ricker inadvertently cutting a 122 kHz tape recorder bias frequency on a master lacquer: http://www.positive-feedback.com/Issue2/mastering.htm.